10.15am: As a key deadline approaches in a prospective cease-fire deal in Syria, new violence threatens to derail negotiations to end the year-long conflict. Under a deal brokered by UN envoy Kofi Annan, Syrian President Bashar al-Assad is to withdraw troops from cities by midnight Monday – just hours away local time. We have live coverage as the deadline approaches. Here are major developments of the last day:

• Turkey has accused Syrian troops of firing across the Turkish border to attack fleeing Syrian refugees. Three Syrians, one Turkish translator and one Turkish policeman were wounded, according to Turkish officials. Tens of thousands of Syrians have poured into Turkey in the last year, and the flow has accelerated dramatically in recent months.

• A Lebanese cameraman was shot dead inside a vehicle at the Lebanese-Syrian border Monday. A colleague from the Al-Jadeed television station said the journalists heard heavy gunfire around them "falling like rain" before the cameramen, Ali Shaaban, was hit in the chest, according to the Associated Press.

• China has called on the Syrian government and opposition to comply with the Annan plan for a ceasefire and negotiations. China, along with Russia, blocked a more powerful UN resolution to end the conflict, however.

• Turkey's deputy foreign minister, Naci Koru, was quoted on Monday as saying tonight's deadline had essentially become irrelevant. "10 April has become void. After Kofi Annan's visit tomorrow [to Turkey] a new stage will start," he was quoted as saying on the website of the Turkish broadcaster NTV.

10.44am: The failure of the United Nations to intervene in Syria in the last bloody months created a deep skepticism about diplomatic peace initiatives before Kofi Annan's announcement last week of a tentative deal for a pullout of troops from cities by Tuesday morning.

That skepticism was seemingly justified Sunday when President Bashar al-Assad called for a signed "guarantee" from opposition groups of an end to violence – as if the onus were on the opposition to stop the shelling of Syrian cities and towns, and as if all that is standing in the way of Assad's desire to secure a cease-fire were the lack of a piece of signed paper.

The deadline for the troop withdrawal is not past. A provisional retreat of some troops could yet set the stage for negotiations that could lead to a cease-fire. Meanwhile Syrian activists are mounting their own campaigns – without the United Nations, without the Arab League – to put pressure on Assad.

#SyriaZEROHOUR is our chance to prove our determination. we will all take to the streets at ZERO HOUR we will not be silenced #Syria— Alexander Page (@AlexanderPageSY) April 9, 2012

One campaign gaining prominence online is the "zero hour" campaign, in which activists, officials, supporters and even uniformed security forces members record videos calling for a coordinated uprising against the Assad regime. The videos run about one minute long. The subjects make no attempts to cover their faces or conceal their identities. Their real names are apparently used. And they all call for the same thing: A unified uprising across the country against the president, at a "zero hour" yet to be declared.

11.10am:Syrian activist Rima Dali, 33, was arrested Sunday in Damascus after she stood in traffic holding a banner that read "Stop killing! We want to build a nation for all Syrians." A companion, Saffana Baqleh, was arrested with her.

Here's video of Rima's protest, with supporters applauding as she stands in the street, holding the banner.

"Stop killing! We want to build a nation for all Syrians". (Rima Dali, arrested in #Syria for pronouncing these words)

"Government and pro-government forces not only executed opposition fighters they had captured, or who had otherwise stopped fighting and posed no threat, but also civilians who likewise posed no threat to the security forces," an HRW statement said.

One of the fighters was injured in his right leg by machine gun fire. He was lying on the street and we could not rescue him as the army was firing and shooting at our position. Then a tank approached, around 15 soldiers with military uniforms surrounded our comrade and started insulting him and kicking him. They were shouting to us that we should surrender or they would kill him. Then they put a black cloth around his eyes, handcuffed him, and one of them shot him dead with an [assault rifle]. When they left, we buried him in the graveyard in the village.

In a new report, "In Cold Blood," Human Rights Watch documents the involvement of Syrian forces in summary executions and violence against civilians.

12.02pm:Russia claims to be promoting a cease-fire in Syria despite its previous opposition to a UN Security Council resolution to stop the violence.

Moscow is "working actively with Damascus in order to begin a political settlement process in [Syria]," Russian Deputy Foreign Minister Gennady Gatilov told state-run Itar-Tass news agency, according to Reuters.

Russia has consistently shielded the Assad regime from claims of unwarranted violence.

"Attempts to force a solution on Syria from outside will lead only to an escalation of tension. Everything must follow from respect for Syria's sovereignty, and violence must be stopped," Gatilov said.

12.52pm: The activist group Local Coordination Committees in Syria has updated its civilian and opposition death toll on Monday to 130. The group tracks daily deaths in Syria on its web site. The numbers rely on local reports and cannot be independently verified.

The Local Coordination Committees in Syria: The number of martyrs has risen, thus far, to 130, among them more... fb.me/1dObXsSTa

Amid reports of new attacks and more than 100 dead, it was clear that the six-point plan of the UN-Arab League envoy to Syria, Kofi Annan, for breaking the deadlock had stalled because of the insistent demand by the president, Bashar al-Assad, for written guarantees that "armed groups" would first lay down their weapons – and their swift refusal to do so.

2.28pm: U.S. Sens. John McCain and Joe Lieberman have joined the diplomatic scramble to secure some sort of ceasefire this week in Syria, meeting with Turkish President Abdullah Gul for more than an hour today in Ankara. No statement was released following the meeting. McCain has tweeted a few photos.

The UN media center quotes Annan's call for the Syrian government to withdraw its forces from cities:

"As we get closer to the Tuesday 10 April deadline, I remind the Syrian Government of the need for full implementation of its commitments and stress that the present escalation of violence is unacceptable," Mr. Annan said.

"I once again call upon both the Government and the opposition to cease all forms of violence by 06:00 Damascus time Thursday, 12 April," he added.

The document, whose authorship is unknown, lays out plans for a coordinated, nationwide "mass demonstration" against the Assad government. The document begins:

What does "Zero Hour" mean?

Zero Hour is the hour that is will be determined, with your help. In this hour, people will come out in mass demonstration in every Syrian city, village, rural area, countryside. No one will remain in their house during this hour. It will include all children, youth, old men and women. No one will remain other than the sick that is not able to stand.

In this hour, we will call everyone to demonstrate in all the main squares. We will come out in the millions to all of Bashar's, the criminal, palaces. We will come out in the millions to the Umayyad Square in Damascus. The floor will shaker under Bashar and his supporters' feet. It will be a calling for the general alarm. It will be a golden opportunity that needs to be taken to our advantage.

2.55pm: NPR's Kelly McEvers has interviewed a soldier who claims to have defected from Assad's security forces. He says he was told that opposition protesters were part of a foreign conspiracy. He describes the mass execution of 30 civilians he says he saw firsthand.

A Kurdish man who calls himself Maxim started his service about a year ago, right about the same time the Syrian uprising began.

In those early days of the uprising last spring, when thousands of Syrians began protesting in the streets, Maxim's commanders told him the protests were actually a conspiracy by a Saudi prince to turn Syria into an Islamic state.

For a while, the soldiers believed it. Maxim says he was part of a special forces unit known as the "shock team."

"We [would] usually break into the area at 4 a.m., when the people are asleep," he says. "We would search the area, house by house, store by store, and we had a list of the wanted people with us."

3.14pm: Under a UN-brokered agreement, Syrian forces are to withdraw from cities by 6a.m. Tuesday. As midnight local time approaches, reports are emerging of nighttime protests against the regime. In the video below the cameraman holds up a sheet of paper that gives the location and date of the protest: Deir Ezzor, Jabilieh, 9 April 2012.

In one instance, when loyalists advanced on the hamlet of Shaturiya, a few miles from Janudieh, a construction worker who had fled to a nearby hilltop saw the troops putting small groups of women and children in front of the approaching tanks.

His son, a 13-year-old who stayed behind in the village when his father fled, was one of those forced to serve as a human shield, according to both of them. The son, slender-framed and matter-of-fact, said he was forced to stand in front of the tanks in the village "for almost six hours, until around midday, without touching food and water."

5.07pm: Activists in Damascus are planning a rally tomorrow to protest the detention of Rima Dali, the woman arrested Sunday for standing outside parliament with a sign reading "Stop the killing! We want to build a country for all Syrians."

To protest against the daily death and killing of Syria, we will gather in front of the Parliament tomorrow at 6 pm. With no slogans, no signs, no flags. Only a red banner reading in white letters: "Stop the killing. We want to build a country for all Syrians"

5.34pm: It's just past midnight in Damascus. We're going to wrap up our live blog coverage of the day's events in Syria. Here's a summary:

• Hopes are dwindling for a UN-brokered truce that was to take effect overnight tonight. As a condition of the truce, Syrian regime forces were to withdraw from "population centers." There has been no indication that such a withdrawal is happening. Instead well over 100 died Monday in continued clashes between forces loyal to President Bashar al-Assad and the opposition.

• The path to a ceasefire is unclear if the current effort fails. Tomorrow's deadline was the highly publicized product of weeks of talks headed up by Kofi Annan acting for the UN and the Arab League. In hours we'll see if the diplomatic process is back to square one.

• At least two were killed and more than 20 wounded when Syrian forces fired across the Turkish border on fleeing refugees, according to the Turkish foreign ministry. Three Syrians, one Turkish translator and one Turkish policeman were wounded inside a refugee camp near the Turkish city of Killis.

• A Lebanese cameraman was shot dead at the Lebanese-Syrian border as he sought to cover the conflict.

• Syrian activists are planning a demonstration outside parliament Tuesday to protest the detention of Rima Dali, an activist arrested in a peace protest Sunday.

• UN Secretary General Ban ki-Moon said he "deplores" the ongoing violence and called for a last-ditch attempt at a truce. Two US senators visited Turkey to try to aid the cease-fire.